1. Field of the Invention
The present invention relates to a semiconductor optical device and a method for producing a semiconductor optical device.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2013-110207 discloses a waveguide-type photodiode in which an optical waveguide is coupled with a front end surface of the photodiode through a butt-joint. The optical waveguide has an upper cladding layer and a core layer doped with Fe in order to decrease the dark current of the photodiode. The concentration of Fe in the core layer is set lower than the saturated concentration in a (100) orientation in order to avoid increasing the propagation loss of the optical waveguide. Furthermore, the Fe concentration of the upper cladding layer is set higher than the saturated concentration in a (100) orientation in order to decrease the dark current of the photodiode.